The present invention is generally related to the field of monitoring and controlling objects, and more particularly, to systems, devices, and methods for remotely monitoring and controlling objects using radio frequency identification (RFID) technology.
A summary of various terms used herein is provided below, followed by a brief overview of known object status tracking systems. RFID refers to technology that uses radio waves to automatically identify people or objects. An object refers to any item used in a facility, work environment, or the like, the presence of which is required to perform work functions such as assembly, processing, design, testing, cleaning, organizing, etc. Examples of objects include hand tools, material handling equipment, parts to be assembled, finished goods, safety equipment, reels of cable, calibration equipment, etc.
The simplest RFID system contains three principal components: an RFID reader, an RFID antenna, and an RFID tag. An RFID reader is a radio transceiver that transmits and receives specifically formatted messages within a certain frequency range. It alternates between ‘transmit’ mode and ‘receive’ mode. An RFID antenna is physically connected to the RFID reader and alternates between transmitting and receiving radio communications. An RFID tag is a solid-state electronic device consisting of a microprocessor and a radio antenna. There are three main types of RFID tags: passive, active, and semi-active. Passive RFID tags contain no power source; they are powered by incident radio waves from the RFID reader. Active tags contain an internal power source such as a battery for microprocessor and transmit functions. Semi-active tags use an internal power source to only run the microprocessor. Passive and semi-active tags do not technically transmit responses back to an RFID reader; rather, they retransmit or backscatter the incoming (incident) radio signal in such a way that the RFID reader is able to uniquely identify a particular tag.
RFID tags are manufactured in a variety of form factors to suit different purposes. For the purposes of disclosing the particulars of this invention, two RFID tag form types are discussed: 1) inlay RFID tags and 2) encapsulated RFID tags. An inlay RFID tag is a simple form factor consisting of an RFID chip and a metallic foil antenna affixed to a thin, flexible substrate such as paper, often printed as adhesive labels. Inlay RFID tags are widely used to track documents and shelved inventory because of their low cost. An inlay RFID tag is typically thin, with a thickness of around 1/10 millimeter. However, inlay RFID tags are not suitable for harsh environments because they are easily damaged by abrasion, liquids, bending, and extremes of temperature and humidity. For harsh environments, encapsulated RFID tags are used. In this type, the chip and antenna are protected within a hardened enclosure, often plastic or ceramic, which protects the tag from damage. This form type also allows for non-flat antenna shapes, which can enhance readability and detection range. An encapsulated RFID tag is generally thick, with a thickness greater than 1 millimeter. A popular shape for encapsulated RFID tags is a rectangular prism.
Certain materials can block or shield the propagation of radio signals to an RFID tag, rendering them undetectable. Such RF opaque materials are termed radio frequency (RF) masking materials. Most metals are RF masking materials, as are many liquids. Certain metamaterials such as carbon impregnated plastic can also act as RF masking materials. RF masking materials are also available as paints, powders, textiles, and foils. Many other materials are transparent to radio waves, or nearly so, and are termed RF transparent materials. Many plastics, ceramics, and textiles are RF transparent materials.
RFID tags are widely used throughout industry to track assets and monitor industrial processes. Typically this involves physically attaching an RFID tag to an object (tagging the object) and entering that pairing in an information storage and retrieval system (ISRS) such as a database. RFID readers and antennas strategically located throughout a workspace continuously interrogate nearby RFID tags, sending information about detected tags to said ISRS. Certain components of said ISRS use collected RFID data to populate a computer user interface with information about RFID-tagged objects. RFID technology is used to track objects by directly affixing an RFID tag to each object, and then recording that association in an information storage and retrieval system (ISRS), e.g. a database. In a typical RFID-based object tracking system, given a sufficient number of RFID antennas connected to strategically placed RFID readers, two types of data can be extracted: 1) the presence or absence of an object, and 2) the approximate location of an object.
Depending upon the design of an RFID tracking system, the presence or absence of an RFID-tagged object within the read range of specific antennas can be determined, from which an approximate location and movement history can be derived.
Conventional RFID tags simply respond to interrogations within their designed frequency ranges. Oftentimes, however, it is desirable for more detailed information about an RFID-tagged object's status to be made known to the ISRS to facilitate optimal decision-making. For example, an RFID-tagged object may need additional inspection, or may be missing a part, or may require special handling, etc. RFID tags capable of storing and transmitting additional status information can also be useful to extend control of objects and processes in a workplace. For example, RFID conveyed status information/data could be used to turn on/off lights, sensors, machinery, or to modify a process such as an assembly line.
Although it is possible to write limited user-defined data to certain types of RFID tags, many users engage read/write-lock controls for security purposes. Furthermore, writing user-defined data to an RFID tag requires the use of an RFID reader and specialized training. Directly writing data to an RFID tag as a means of conveying the status of an RFID-tracked object adds delay, cost and complexity which disadvantages for the rapid pace of a workplace.
Since the RFID-tagged object is already within proximity of an RFID system, an improved RFID-based system for quickly, simply, and cheaply changing and conveying the status of RFID-tagged objects would enhance the overall value of RFID tracking systems.